Primary intrapulmonary neurogenic tumors can originate anywhere in the thorax. They are often found in the chest wall and the mediastinum. However, it is quite rare to find them in the bronchi or within the pulmonary parenchyma. In one series of 1664 primary pulmonary tumors, only 4 intrapulmonary neurogenic tumors were identified (0.2%). 1 Most intrapulmonary neurogenic tumors were neurofibromas, with schwannomas accounting for only 25% of the tumors. 2 We present a rare case of multiple endobronchial schwannomas at the bronchial spur of 2 different sites.
A 77-year-old asymptomatic man was admitted to Hokkaido University Medical Hospital reporting daytime sleepiness as a result of obstructive-type sleep apnea syndrome (O-SAS). Six years previously (at 71 years of age), he had been diagnosed as having acromegaly caused by pituitary adenoma, in addition to O-SAS caused by obesity and macroglossia resulting from acromegaly. He subsequently underwent transsphenoidal surgery for the pituitary adenoma. He was 155 cm in height and 73 kg in weight (body mass index 31). His chest was clear on auscultation. Laboratory findings, including growth hormone and tumor markers, were all within normal limits. Chest x-ray revealed no abnormalities. Computed tomography scans of the chest showed areas of low attenuation, indicating the presence of pulmonary emphysema. Because he had been smoking 3 packs of cigarettes a day for 50 years (150 pack-year), bronchoscopic examination was performed. This revealed thickening of the bronchial spur with hypervascularity and granular redness of the bronchial mucosa at 2 different sites; one was located at the right middle/lower lobe bronchi and the other at the right basalis anterior/basalis lateralis segmental bronchi (Fig. 1). Histologic examination of transbronchial biopsy specimens taken from both lesions revealed bland-looking spindle cell proliferation with vague nuclear palisading and slight myxoid changes in the tunica propria (Fig. 2). The mucosal epithelium displayed squamous metaplasia. Immunohistochemically, tumor cells were positive for S-100 protein but negative for smooth muscle actin (Fig. 3). These findings were consistent with schwannoma. The patient showed no evidence of von Recklinghausen's disease or schwannoma in other organs. Because both lesions were considered to be benign endobronchial schwannomas with no symptoms, the patient was periodically followed without any treatment in our outpatient clinic. Bronchoscopic examination was performed twice in 2 years during the follow up, and no remarkable changes in size or appearance have been observed in either lesion.
Primary endobronchial schwannomas are a very rare type of benign lung tumor. We found approximately 90 cases of intrapulmonary schwannomas in a search of the English-language literature. These tumors occur predominantly in women, and all age groups can be affected. 2 Since the first description of a case with schwannoma of the tracheobronchial tree in 1951, 3 tissue culture studies have confirmed that this tumor originates in the Schwann cells of the nerve sheath. 4 Although the nerves in which endobronchial schwannomas arise are unknown, they might be derived from vagal nerves in the bronchial wall. 5 We identified 20 cases of endobronchial schwannomas in a search of the English-language literature. To the best of our knowledge, this is the first reported case in which endobronchial schwannomas arose at the bronchial spur of 2 different sites.
Most endobronchial schwannomas are asymptomatic and tend to be discovered on routine radiographic examination of the chest. 1 At bronchoscopy, endobronchial schwannomas are seen as nodules covered with normal bronchial mucosa bulging into the tracheobronchial lumen or raising the bronchial mucosa with hypervascularity at the spur of the bronchus, as in the present case. 3,6 Squamous metaplasia observed on the surface of schwannomas in the present case might be caused either by proliferation of schwannoma in submucosal cells or by cigarette smoking. Moreover, multiple endobronchial schwannomas in the present case might be caused by the proliferation of Schwann cells resulting from cigarette smoking followed by inflammation of the bronchial mucosa.
Schwannomas are composed of 2 distinct types of tissue; one is formed of cells with elongated nuclei aligned in parallel rows and separated from similar rows by clear spaces containing fine fibrils, suggesting a Verocay body (Antoni A). Admixed with this or in separate areas, the tumor is comprised of a loose texture with elongated cells arranged in an irregular fashion and separated from one another by myxomatous stroma (Antoni B). 2 The presence of Antoni A and B areas is very helpful for pathologic diagnosis, but it is more useful to demonstrate the neurogenic nature in immunohistochemical study. 7 Identification of S-100 protein in both nucleus and cytoplasm of the tumor cells using polyclonal S-100 antisera supports the schwannian origin of this neoplasm. 7
Some cases have undergone operative procedures such as pneumonectomy and lobectomy, 8 whereas others have been conservatively treated by bronchoscopic polypectomy 9 and endoscopic Nd-YAG laser treatment. 10 The clinical course of the present case was followed without any treatment as a result of the lack of respiratory symptoms and because no malignant markers such as pleomorphic nuclei or mitosis were found in the tumor.
Endobronchial schwannoma accompanied by acromegaly, like in the present case, has not been reported to date, and a causal relationship between endobronchial schwannoma and acromegaly was not apparent.
In summary, we have described a rare case of endobronchial schwannoma of the bronchial spur at 2 different sites. Because endobronchial schwannomas, such as the present case, are sometimes seen as tumors raising the bronchial mucosa with hypervascularity at the bronchial spur, they should be kept in mind when considering differential diagnoses for endobronchial tumors.
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